/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Copyright (c) 2011 The FreeBSD Foundation
 *
 * Copyright (c) 2023 Dag-Erling Smørgrav
 *
 * Portions of this software were developed by David Chisnall
 * under sponsorship from the FreeBSD Foundation.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "namespace.h"
#include <ctype.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdarg.h>
#include <string.h>
#include <wchar.h>
#include <wctype.h>
#include "un-namespace.h"

#include "collate.h"
#include "libc_private.h"
#include "local.h"
#include "xlocale_private.h"

#include <locale.h>

#define BUF             513     /* Maximum length of numeric string. */

/*
 * Flags used during conversion.
 */
#define LONG            0x01    /* l: long or double */
#define LONGDBL         0x02    /* L: long double */
#define SHORT           0x04    /* h: short */
#define SUPPRESS        0x08    /* *: suppress assignment */
#define POINTER         0x10    /* p: void * (as hex) */
#define NOSKIP          0x20    /* [ or c: do not skip blanks */
#define FASTINT         0x200   /* wfN: int_fastN_t */
#define LONGLONG        0x400   /* ll: long long (+ deprecated q: quad) */
#define INTMAXT         0x800   /* j: intmax_t */
#define PTRDIFFT        0x1000  /* t: ptrdiff_t */
#define SIZET           0x2000  /* z: size_t */
#define SHORTSHORT      0x4000  /* hh: char */
#define UNSIGNED        0x8000  /* %[oupxX] conversions */

/*
 * Conversion types.
 */
#define CT_CHAR         0       /* %c conversion */
#define CT_CCL          1       /* %[...] conversion */
#define CT_STRING       2       /* %s conversion */
#define CT_INT          3       /* %[dioupxX] conversion */
#define CT_FLOAT        4       /* %[efgEFG] conversion */

static const u_char *__sccl(char *, const u_char *);
static int parsefloat(FILE *, char *, char *, locale_t);

__weak_reference(__vfscanf, vfscanf);

/*
 * Conversion functions are passed a pointer to this object instead of
 * a real parameter to indicate that the assignment-suppression (*)
 * flag was specified.  We could use a NULL pointer to indicate this,
 * but that would mask bugs in applications that call scanf() with a
 * NULL pointer.
 */
static const int suppress;
#define SUPPRESS_PTR    ((void *)&suppress)

static const mbstate_t initial_mbs;

/*
 * The following conversion functions return the number of characters consumed,
 * or -1 on input failure.  Character class conversion returns 0 on match
 * failure.
 */

static __inline int
convert_char(FILE *fp, char * p, int width)
{
        int n;

        if (p == SUPPRESS_PTR) {
                size_t sum = 0;
                for (;;) {
                        if ((n = fp->_r) < width) {
                                sum += n;
                                width -= n;
                                fp->_p += n;
                                if (__srefill(fp)) {
                                        if (sum == 0)
                                                return (-1);
                                        break;
                                }
                        } else {
                                sum += width;
                                fp->_r -= width;
                                fp->_p += width;
                                break;
                        }
                }
                return (sum);
        } else {
                size_t r = __fread(p, 1, width, fp);

                if (r == 0)
                        return (-1);
                return (r);
        }
}

static __inline int
convert_wchar(FILE *fp, wchar_t *wcp, int width, locale_t locale)
{
        mbstate_t mbs;
        int n, nread;
        wint_t wi;

        mbs = initial_mbs;
        n = 0;
        while (width-- != 0 &&
            (wi = __fgetwc_mbs(fp, &mbs, &nread, locale)) != WEOF) {
                if (wcp != SUPPRESS_PTR)
                        *wcp++ = (wchar_t)wi;
                n += nread;
        }
        if (n == 0)
                return (-1);
        return (n);
}

static __inline int
convert_ccl(FILE *fp, char * p, int width, const char *ccltab)
{
        char *p0;
        int n;

        if (p == SUPPRESS_PTR) {
                n = 0;
                while (ccltab[*fp->_p]) {
                        n++, fp->_r--, fp->_p++;
                        if (--width == 0)
                                break;
                        if (fp->_r <= 0 && __srefill(fp)) {
                                if (n == 0)
                                        return (-1);
                                break;
                        }
                }
        } else {
                p0 = p;
                while (ccltab[*fp->_p]) {
                        fp->_r--;
                        *p++ = *fp->_p++;
                        if (--width == 0)
                                break;
                        if (fp->_r <= 0 && __srefill(fp)) {
                                if (p == p0)
                                        return (-1);
                                break;
                        }
                }
                n = p - p0;
                if (n == 0)
                        return (0);
                *p = 0;
        }
        return (n);
}

static __inline int
convert_wccl(FILE *fp, wchar_t *wcp, int width, const char *ccltab,
    locale_t locale)
{
        mbstate_t mbs;
        wint_t wi;
        int n, nread;

        mbs = initial_mbs;
        n = 0;
        if (wcp == SUPPRESS_PTR) {
                while ((wi = __fgetwc_mbs(fp, &mbs, &nread, locale)) != WEOF &&
                    width-- != 0 && ccltab[wctob(wi)])
                        n += nread;
                if (wi != WEOF)
                        __ungetwc(wi, fp, __get_locale());
        } else {
                while ((wi = __fgetwc_mbs(fp, &mbs, &nread, locale)) != WEOF &&
                    width-- != 0 && ccltab[wctob(wi)]) {
                        *wcp++ = (wchar_t)wi;
                        n += nread;
                }
                if (wi != WEOF)
                        __ungetwc(wi, fp, __get_locale());
                if (n == 0)
                        return (0);
                *wcp = 0;
        }
        return (n);
}

static __inline int
convert_string(FILE *fp, char * p, int width)
{
        char *p0;
        int n;

        if (p == SUPPRESS_PTR) {
                n = 0;
                while (!isspace(*fp->_p)) {
                        n++, fp->_r--, fp->_p++;
                        if (--width == 0)
                                break;
                        if (fp->_r <= 0 && __srefill(fp))
                                break;
                }
        } else {
                p0 = p;
                while (!isspace(*fp->_p)) {
                        fp->_r--;
                        *p++ = *fp->_p++;
                        if (--width == 0)
                                break;
                        if (fp->_r <= 0 && __srefill(fp))
                                break;
                }
                *p = 0;
                n = p - p0;
        }
        return (n);
}

static __inline int
convert_wstring(FILE *fp, wchar_t *wcp, int width, locale_t locale)
{
        mbstate_t mbs;
        wint_t wi;
        int n, nread;

        mbs = initial_mbs;
        n = 0;
        if (wcp == SUPPRESS_PTR) {
                while ((wi = __fgetwc_mbs(fp, &mbs, &nread, locale)) != WEOF &&
                    width-- != 0 && !iswspace(wi))
                        n += nread;
                if (wi != WEOF)
                        __ungetwc(wi, fp, __get_locale());
        } else {
                while ((wi = __fgetwc_mbs(fp, &mbs, &nread, locale)) != WEOF &&
                    width-- != 0 && !iswspace(wi)) {
                        *wcp++ = (wchar_t)wi;
                        n += nread;
                }
                if (wi != WEOF)
                        __ungetwc(wi, fp, __get_locale());
                *wcp = '\0';
        }
        return (n);
}

enum parseint_state {
        begin,
        havesign,
        havezero,
        haveprefix,
        any,
};

static __inline int
parseint_fsm(int c, enum parseint_state *state, int *base)
{
        switch (c) {
        case '+':
        case '-':
                if (*state == begin) {
                        *state = havesign;
                        return 1;
                }
                break;
        case '0':
                if (*state == begin || *state == havesign) {
                        *state = havezero;
                        return 1;
                }
                /* FALL THROUGH */
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
                if (*state == havezero && *base == 0) {
                        *base = 8;
                }
                /* FALL THROUGH */
        case '8':
        case '9':
                if (*state == begin ||
                    *state == havesign) {
                        if (*base == 0) {
                                *base = 10;
                        }
                }
                if (*state == begin ||
                    *state == havesign ||
                    *state == havezero ||
                    *state == haveprefix ||
                    *state == any) {
                        if (*base > c - '0') {
                                *state = any;
                                return 1;
                        }
                }
                break;
        case 'b':
                if (*state == havezero) {
                        if (*base == 0 || *base == 2) {
                                *state = haveprefix;
                                *base = 2;
                                return 1;
                        }
                }
                /* FALL THROUGH */
        case 'a':
        case 'c':
        case 'd':
        case 'e':
        case 'f':
                if (*state == begin ||
                    *state == havesign ||
                    *state == havezero ||
                    *state == haveprefix ||
                    *state == any) {
                        if (*base > c - 'a' + 10) {
                                *state = any;
                                return 1;
                        }
                }
                break;
        case 'B':
                if (*state == havezero) {
                        if (*base == 0 || *base == 2) {
                                *state = haveprefix;
                                *base = 2;
                                return 1;
                        }
                }
                /* FALL THROUGH */
        case 'A':
        case 'C':
        case 'D':
        case 'E':
        case 'F':
                if (*state == begin ||
                    *state == havesign ||
                    *state == havezero ||
                    *state == haveprefix ||
                    *state == any) {
                        if (*base > c - 'A' + 10) {
                                *state = any;
                                return 1;
                        }
                }
                break;
        case 'x':
        case 'X':
                if (*state == havezero) {
                        if (*base == 0 || *base == 16) {
                                *state = haveprefix;
                                *base = 16;
                                return 1;
                        }
                }
                break;
        }
        return 0;
}

/*
 * Read an integer, storing it in buf.
 *
 * Return 0 on a match failure, and the number of characters read
 * otherwise.
 */
static __inline int
parseint(FILE *fp, char * __restrict buf, int width, int base)
{
        enum parseint_state state = begin;
        char *p;
        int c;

        for (p = buf; width; width--) {
                c = __sgetc(fp);
                if (c == EOF)
                        break;
                if (!parseint_fsm(c, &state, &base))
                        break;
                *p++ = c;
        }
        /*
         * If we only had a sign, push it back.  If we only had a 0b or 0x
         * prefix (possibly preceded by a sign), we view it as "0" and
         * push back the letter.  In all other cases, if we stopped
         * because we read a non-number character, push it back.
         */
        if (state == havesign) {
                p--;
                (void) __ungetc(*(u_char *)p, fp);
        } else if (state == haveprefix) {
                p--;
                (void) __ungetc(c, fp);
        } else if (width && c != EOF) {
                (void) __ungetc(c, fp);
        }
        return (p - buf);
}

/*
 * __vfscanf - MT-safe version
 */
int
__vfscanf(FILE *fp, char const *fmt0, va_list ap)
{
        int ret;

        FLOCKFILE_CANCELSAFE(fp);
        ret = __svfscanf(fp, __get_locale(), fmt0, ap);
        FUNLOCKFILE_CANCELSAFE();
        return (ret);
}
int
vfscanf_l(FILE *fp, locale_t locale, char const *fmt0, va_list ap)
{
        int ret;
        FIX_LOCALE(locale);

        FLOCKFILE_CANCELSAFE(fp);
        ret = __svfscanf(fp, locale, fmt0, ap);
        FUNLOCKFILE_CANCELSAFE();
        return (ret);
}

/*
 * __svfscanf - non-MT-safe version of __vfscanf
 */
int
__svfscanf(FILE *fp, locale_t locale, const char *fmt0, va_list ap)
{
#define GETARG(type)    ((flags & SUPPRESS) ? SUPPRESS_PTR : va_arg(ap, type))
        const u_char *fmt = (const u_char *)fmt0;
        int c;                  /* character from format, or conversion */
        size_t width;           /* field width, or 0 */
        int flags;              /* flags as defined above */
        int nassigned;          /* number of fields assigned */
        int nconversions;       /* number of conversions */
        int nr;                 /* characters read by the current conversion */
        int nread;              /* number of characters consumed from fp */
        int base;               /* base argument to conversion function */
        char ccltab[256];       /* character class table for %[...] */
        char buf[BUF];          /* buffer for numeric conversions */

        ORIENT(fp, -1);

        nassigned = 0;
        nconversions = 0;
        nread = 0;
        for (;;) {
                c = *fmt++;
                if (c == 0)
                        return (nassigned);
                if (isspace(c)) {
                        while ((fp->_r > 0 || __srefill(fp) == 0) && isspace(*fp->_p))
                                nread++, fp->_r--, fp->_p++;
                        continue;
                }
                if (c != '%')
                        goto literal;
                width = 0;
                flags = 0;
                /*
                 * switch on the format.  continue if done;
                 * break once format type is derived.
                 */
again:          c = *fmt++;
                switch (c) {
                case '%':
literal:
                        if (fp->_r <= 0 && __srefill(fp))
                                goto input_failure;
                        if (*fp->_p != c)
                                goto match_failure;
                        fp->_r--, fp->_p++;
                        nread++;
                        continue;

                case '*':
                        flags |= SUPPRESS;
                        goto again;
                case 'j':
                        flags |= INTMAXT;
                        goto again;
                case 'l':
                        if (flags & LONG) {
                                flags &= ~LONG;
                                flags |= LONGLONG;
                        } else
                                flags |= LONG;
                        goto again;
                case 'q':
                        flags |= LONGLONG;      /* not quite */
                        goto again;
                case 't':
                        flags |= PTRDIFFT;
                        goto again;
                case 'w':
                        /*
                         * Fixed-width integer types.  On all platforms we
                         * support, int8_t is equivalent to char, int16_t
                         * is equivalent to short, int32_t is equivalent
                         * to int, int64_t is equivalent to long long int.
                         * Furthermore, int_fast8_t, int_fast16_t and
                         * int_fast32_t are equivalent to int, and
                         * int_fast64_t is equivalent to long long int.
                         */
                        flags &= ~(SHORTSHORT|SHORT|LONG|LONGLONG|SIZET|INTMAXT|PTRDIFFT);
                        if (fmt[0] == 'f') {
                                flags |= FASTINT;
                                fmt++;
                        } else {
                                flags &= ~FASTINT;
                        }
                        if (fmt[0] == '8') {
                                if (!(flags & FASTINT))
                                        flags |= SHORTSHORT;
                                else
                                        /* no flag set = 32 */ ;
                                fmt += 1;
                        } else if (fmt[0] == '1' && fmt[1] == '6') {
                                if (!(flags & FASTINT))
                                        flags |= SHORT;
                                else
                                        /* no flag set = 32 */ ;
                                fmt += 2;
                        } else if (fmt[0] == '3' && fmt[1] == '2') {
                                /* no flag set = 32 */ ;
                                fmt += 2;
                        } else if (fmt[0] == '6' && fmt[1] == '4') {
                                flags |= LONGLONG;
                                fmt += 2;
                        } else {
                                goto match_failure;
                        }
                        goto again;
                case 'z':
                        flags |= SIZET;
                        goto again;
                case 'L':
                        flags |= LONGDBL;
                        goto again;
                case 'h':
                        if (flags & SHORT) {
                                flags &= ~SHORT;
                                flags |= SHORTSHORT;
                        } else
                                flags |= SHORT;
                        goto again;

                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                        width = width * 10 + c - '0';
                        goto again;

                /*
                 * Conversions.
                 */
                case 'B':
                case 'b':
                        c = CT_INT;
                        flags |= UNSIGNED;
                        base = 2;
                        break;

                case 'd':
                        c = CT_INT;
                        base = 10;
                        break;

                case 'i':
                        c = CT_INT;
                        base = 0;
                        break;

                case 'o':
                        c = CT_INT;
                        flags |= UNSIGNED;
                        base = 8;
                        break;

                case 'u':
                        c = CT_INT;
                        flags |= UNSIGNED;
                        base = 10;
                        break;

                case 'X':
                case 'x':
                        c = CT_INT;
                        flags |= UNSIGNED;
                        base = 16;
                        break;

                case 'A': case 'E': case 'F': case 'G':
                case 'a': case 'e': case 'f': case 'g':
                        c = CT_FLOAT;
                        break;

                case 'S':
                        flags |= LONG;
                        /* FALLTHROUGH */
                case 's':
                        c = CT_STRING;
                        break;

                case '[':
                        fmt = __sccl(ccltab, fmt);
                        flags |= NOSKIP;
                        c = CT_CCL;
                        break;

                case 'C':
                        flags |= LONG;
                        /* FALLTHROUGH */
                case 'c':
                        flags |= NOSKIP;
                        c = CT_CHAR;
                        break;

                case 'p':       /* pointer format is like hex */
                        flags |= POINTER;
                        c = CT_INT;             /* assumes sizeof(uintmax_t) */
                        flags |= UNSIGNED;      /*      >= sizeof(uintptr_t) */
                        base = 16;
                        break;

                case 'n':
                        if (flags & SUPPRESS)   /* ??? */
                                continue;
                        if (flags & SHORTSHORT)
                                *va_arg(ap, char *) = nread;
                        else if (flags & SHORT)
                                *va_arg(ap, short *) = nread;
                        else if (flags & LONG)
                                *va_arg(ap, long *) = nread;
                        else if (flags & LONGLONG)
                                *va_arg(ap, long long *) = nread;
                        else if (flags & INTMAXT)
                                *va_arg(ap, intmax_t *) = nread;
                        else if (flags & SIZET)
                                *va_arg(ap, size_t *) = nread;
                        else if (flags & PTRDIFFT)
                                *va_arg(ap, ptrdiff_t *) = nread;
                        else
                                *va_arg(ap, int *) = nread;
                        continue;

                default:
                        goto match_failure;

                /*
                 * Disgusting backwards compatibility hack.     XXX
                 */
                case '\0':      /* compat */
                        return (EOF);
                }

                /*
                 * We have a conversion that requires input.
                 */
                if (fp->_r <= 0 && __srefill(fp))
                        goto input_failure;

                /*
                 * Consume leading white space, except for formats
                 * that suppress this.
                 */
                if ((flags & NOSKIP) == 0) {
                        while (isspace(*fp->_p)) {
                                nread++;
                                if (--fp->_r > 0)
                                        fp->_p++;
                                else if (__srefill(fp))
                                        goto input_failure;
                        }
                        /*
                         * Note that there is at least one character in
                         * the buffer, so conversions that do not set NOSKIP
                         * ca no longer result in an input failure.
                         */
                }

                /*
                 * Do the conversion.
                 */
                switch (c) {

                case CT_CHAR:
                        /* scan arbitrary characters (sets NOSKIP) */
                        if (width == 0)
                                width = 1;
                        if (flags & LONG) {
                                nr = convert_wchar(fp, GETARG(wchar_t *),
                                    width, locale);
                        } else {
                                nr = convert_char(fp, GETARG(char *), width);
                        }
                        if (nr < 0)
                                goto input_failure;
                        break;

                case CT_CCL:
                        /* scan a (nonempty) character class (sets NOSKIP) */
                        if (width == 0)
                                width = (size_t)~0;     /* `infinity' */
                        if (flags & LONG) {
                                nr = convert_wccl(fp, GETARG(wchar_t *), width,
                                    ccltab, locale);
                        } else {
                                nr = convert_ccl(fp, GETARG(char *), width,
                                    ccltab);
                        }
                        if (nr <= 0) {
                                if (nr < 0)
                                        goto input_failure;
                                else /* nr == 0 */
                                        goto match_failure;
                        }
                        break;

                case CT_STRING:
                        /* like CCL, but zero-length string OK, & no NOSKIP */
                        if (width == 0)
                                width = (size_t)~0;
                        if (flags & LONG) {
                                nr = convert_wstring(fp, GETARG(wchar_t *),
                                    width, locale);
                        } else {
                                nr = convert_string(fp, GETARG(char *), width);
                        }
                        if (nr < 0)
                                goto input_failure;
                        break;

                case CT_INT:
                        /* scan an integer as if by the conversion function */
#ifdef hardway
                        if (width == 0 || width > sizeof(buf) - 1)
                                width = sizeof(buf) - 1;
#else
                        /* size_t is unsigned, hence this optimisation */
                        if (--width > sizeof(buf) - 2)
                                width = sizeof(buf) - 2;
                        width++;
#endif
                        nr = parseint(fp, buf, width, base);
                        if (nr == 0)
                                goto match_failure;
                        if ((flags & SUPPRESS) == 0) {
                                uintmax_t res;

                                buf[nr] = '\0';
                                if ((flags & UNSIGNED) == 0)
                                    res = strtoimax_l(buf, (char **)NULL, base, locale);
                                else
                                    res = strtoumax_l(buf, (char **)NULL, base, locale);
                                if (flags & POINTER)
                                        *va_arg(ap, void **) =
                                                        (void *)(uintptr_t)res;
                                else if (flags & SHORTSHORT)
                                        *va_arg(ap, char *) = res;
                                else if (flags & SHORT)
                                        *va_arg(ap, short *) = res;
                                else if (flags & LONG)
                                        *va_arg(ap, long *) = res;
                                else if (flags & LONGLONG)
                                        *va_arg(ap, long long *) = res;
                                else if (flags & INTMAXT)
                                        *va_arg(ap, intmax_t *) = res;
                                else if (flags & PTRDIFFT)
                                        *va_arg(ap, ptrdiff_t *) = res;
                                else if (flags & SIZET)
                                        *va_arg(ap, size_t *) = res;
                                else
                                        *va_arg(ap, int *) = res;
                        }
                        break;

                case CT_FLOAT:
                        /* scan a floating point number as if by strtod */
                        if (width == 0 || width > sizeof(buf) - 1)
                                width = sizeof(buf) - 1;
                        nr = parsefloat(fp, buf, buf + width, locale);
                        if (nr == 0)
                                goto match_failure;
                        if ((flags & SUPPRESS) == 0) {
                                if (flags & LONGDBL) {
                                        long double res = strtold_l(buf, NULL,
                                            locale);
                                        *va_arg(ap, long double *) = res;
                                } else if (flags & LONG) {
                                        double res = strtod_l(buf, NULL,
                                            locale);
                                        *va_arg(ap, double *) = res;
                                } else {
                                        float res = strtof_l(buf, NULL, locale);
                                        *va_arg(ap, float *) = res;
                                }
                        }
                        break;
                }
                if (!(flags & SUPPRESS))
                        nassigned++;
                nread += nr;
                nconversions++;
        }
input_failure:
        return (nconversions != 0 ? nassigned : EOF);
match_failure:
        return (nassigned);
}

/*
 * Fill in the given table from the scanset at the given format
 * (just after `[').  Return a pointer to the character past the
 * closing `]'.  The table has a 1 wherever characters should be
 * considered part of the scanset.
 */
static const u_char *
__sccl(char *tab, const u_char *fmt)
{
        int c, n, v, i;
        struct xlocale_collate *table =
                (struct xlocale_collate*)__get_locale()->components[XLC_COLLATE];

        /* first `clear' the whole table */
        c = *fmt++;             /* first char hat => negated scanset */
        if (c == '^') {
                v = 1;          /* default => accept */
                c = *fmt++;     /* get new first char */
        } else
                v = 0;          /* default => reject */

        /* XXX: Will not work if sizeof(tab*) > sizeof(char) */
        (void) memset(tab, v, 256);

        if (c == 0)
                return (fmt - 1);/* format ended before closing ] */

        /*
         * Now set the entries corresponding to the actual scanset
         * to the opposite of the above.
         *
         * The first character may be ']' (or '-') without being special;
         * the last character may be '-'.
         */
        v = 1 - v;
        for (;;) {
                tab[c] = v;             /* take character c */
doswitch:
                n = *fmt++;             /* and examine the next */
                switch (n) {

                case 0:                 /* format ended too soon */
                        return (fmt - 1);

                case '-':
                        /*
                         * A scanset of the form
                         *      [01+-]
                         * is defined as `the digit 0, the digit 1,
                         * the character +, the character -', but
                         * the effect of a scanset such as
                         *      [a-zA-Z0-9]
                         * is implementation defined.  The V7 Unix
                         * scanf treats `a-z' as `the letters a through
                         * z', but treats `a-a' as `the letter a, the
                         * character -, and the letter a'.
                         *
                         * For compatibility, the `-' is not considered
                         * to define a range if the character following
                         * it is either a close bracket (required by ANSI)
                         * or is not numerically greater than the character
                         * we just stored in the table (c).
                         */
                        n = *fmt;
                        if (n == ']'
                            || (table->__collate_load_error ? n < c :
                                __collate_range_cmp(n, c) < 0
                               )
                           ) {
                                c = '-';
                                break;  /* resume the for(;;) */
                        }
                        fmt++;
                        /* fill in the range */
                        if (table->__collate_load_error) {
                                do {
                                        tab[++c] = v;
                                } while (c < n);
                        } else {
                                for (i = 0; i < 256; i ++)
                                        if (__collate_range_cmp(c, i) <= 0 &&
                                            __collate_range_cmp(i, n) <= 0
                                           )
                                                tab[i] = v;
                        }
#if 1   /* XXX another disgusting compatibility hack */
                        c = n;
                        /*
                         * Alas, the V7 Unix scanf also treats formats
                         * such as [a-c-e] as `the letters a through e'.
                         * This too is permitted by the standard....
                         */
                        goto doswitch;
#else
                        c = *fmt++;
                        if (c == 0)
                                return (fmt - 1);
                        if (c == ']')
                                return (fmt);
#endif
                        break;

                case ']':               /* end of scanset */
                        return (fmt);

                default:                /* just another character */
                        c = n;
                        break;
                }
        }
        /* NOTREACHED */
}

static int
parsefloat(FILE *fp, char *buf, char *end, locale_t locale)
{
        char *commit, *p;
        int infnanpos = 0, decptpos = 0;
        enum {
                S_START, S_GOTSIGN, S_INF, S_NAN, S_DONE, S_MAYBEHEX,
                S_DIGITS, S_DECPT, S_FRAC, S_EXP, S_EXPDIGITS
        } state = S_START;
        unsigned char c;
        const char *decpt = localeconv_l(locale)->decimal_point;
        _Bool gotmantdig = 0, ishex = 0;

        /*
         * We set commit = p whenever the string we have read so far
         * constitutes a valid representation of a floating point
         * number by itself.  At some point, the parse will complete
         * or fail, and we will ungetc() back to the last commit point.
         * To ensure that the file offset gets updated properly, it is
         * always necessary to read at least one character that doesn't
         * match; thus, we can't short-circuit "infinity" or "nan(...)".
         */
        commit = buf - 1;
        for (p = buf; p < end; ) {
                c = *fp->_p;
reswitch:
                switch (state) {
                case S_START:
                        state = S_GOTSIGN;
                        if (c == '-' || c == '+')
                                break;
                        else
                                goto reswitch;
                case S_GOTSIGN:
                        switch (c) {
                        case '0':
                                state = S_MAYBEHEX;
                                commit = p;
                                break;
                        case 'I':
                        case 'i':
                                state = S_INF;
                                break;
                        case 'N':
                        case 'n':
                                state = S_NAN;
                                break;
                        default:
                                state = S_DIGITS;
                                goto reswitch;
                        }
                        break;
                case S_INF:
                        if (infnanpos > 6 ||
                            (c != "nfinity"[infnanpos] &&
                             c != "NFINITY"[infnanpos]))
                                goto parsedone;
                        if (infnanpos == 1 || infnanpos == 6)
                                commit = p;     /* inf or infinity */
                        infnanpos++;
                        break;
                case S_NAN:
                        switch (infnanpos) {
                        case 0:
                                if (c != 'A' && c != 'a')
                                        goto parsedone;
                                break;
                        case 1:
                                if (c != 'N' && c != 'n')
                                        goto parsedone;
                                else
                                        commit = p;
                                break;
                        case 2:
                                if (c != '(')
                                        goto parsedone;
                                break;
                        default:
                                if (c == ')') {
                                        commit = p;
                                        state = S_DONE;
                                } else if (!isalnum(c) && c != '_')
                                        goto parsedone;
                                break;
                        }
                        infnanpos++;
                        break;
                case S_DONE:
                        goto parsedone;
                case S_MAYBEHEX:
                        state = S_DIGITS;
                        if (c == 'X' || c == 'x') {
                                ishex = 1;
                                break;
                        } else {        /* we saw a '0', but no 'x' */
                                gotmantdig = 1;
                                goto reswitch;
                        }
                case S_DIGITS:
                        if ((ishex && isxdigit(c)) || isdigit(c)) {
                                gotmantdig = 1;
                                commit = p;
                                break;
                        } else {
                                state = S_DECPT;
                                goto reswitch;
                        }
                case S_DECPT:
                        if (c == decpt[decptpos]) {
                                if (decpt[++decptpos] == '\0') {
                                        /* We read the complete decpt seq. */
                                        state = S_FRAC;
                                        if (gotmantdig)
                                                commit = p;
                                }
                                break;
                        } else if (!decptpos) {
                                /* We didn't read any decpt characters. */
                                state = S_FRAC;
                                goto reswitch;
                        } else {
                                /*
                                 * We read part of a multibyte decimal point,
                                 * but the rest is invalid, so bail.
                                 */
                                goto parsedone;
                        }
                case S_FRAC:
                        if (((c == 'E' || c == 'e') && !ishex) ||
                            ((c == 'P' || c == 'p') && ishex)) {
                                if (!gotmantdig)
                                        goto parsedone;
                                else
                                        state = S_EXP;
                        } else if ((ishex && isxdigit(c)) || isdigit(c)) {
                                commit = p;
                                gotmantdig = 1;
                        } else
                                goto parsedone;
                        break;
                case S_EXP:
                        state = S_EXPDIGITS;
                        if (c == '-' || c == '+')
                                break;
                        else
                                goto reswitch;
                case S_EXPDIGITS:
                        if (isdigit(c))
                                commit = p;
                        else
                                goto parsedone;
                        break;
                default:
                        abort();
                }
                *p++ = c;
                if (--fp->_r > 0)
                        fp->_p++;
                else if (__srefill(fp))
                        break;  /* EOF */
        }

parsedone:
        while (commit < --p)
                __ungetc(*(u_char *)p, fp);
        *++commit = '\0';
        return (commit - buf);
}